The present invention relates to an apparatus for use in the decontamination of an apparatus, such as an electrical transformer, contaminated with polychlorinated biphenyls (PCBs). More specifically, the present invention relates to an apparatus for decontaminating PCB contaminated electrical transformers characterized by its simplicity and ease of operation and primarily by its compact size and its ability to manage heat and operate without the need for someone to be in attendance. In particular, the present invention relates to a simple and easily operated apparatus for decontaminating PCB contaminated transformers which is designed such that the heat which is generated during the operation of the electrical transformer or portion of the heat which is used in the removal of the PCBs from the transformer fluid is used to enhance the rate of removal of the PCBs from the electrical transformer.
For many years PCBs have been used as an insulation or dielectric fluid in the electrical apparatus industry as a safe, fire-resistant material. In the late '60s and early '70s, it was discovered that PCBs were hazardous environmental contaminants, and their use was discontinued; however, by that time many pieces of electrical apparatus had been built using PCBs. The primary use of PCBs is in electrical transformers and electrical capacitors as a coolant dielectric fluid. Accordingly, the need has risen to economically remove the PCBs from such electrical apparatus as electrical transformers. Transformers using PCBs as the dielectric or coolant fluid all had a common construction in that they contained a cellulosic material as insulation, usually paper, wrapped on and around a wire that comprises the majority of the core of the transformer. Also commonly included in the construction of such transformers are wood structures acting as insulators. Because of the porosity of these two major items used in construction of the transformer, the interior of the transformer acted somewhat like a sponge and the PCBs became impregnated into these materials. Consequently, attempts to simply remove the PCBs and in a single operation refill the transformer with another coolant dielectric fluid has failed to reduce the PCBs below the accepted U.S. Environmental Protection Agency (EPA) levels for a non-PCB transformer. To be reclassified as a non-PCB transformer by EPA standards, the level of PCBs in the transformer must be maintained at less than 50 parts per million (ppm) for at least three months. Thus, to reach these levels and satisfy the non-PCB standard, the PCBs which have become impregnated in the materials of the core as well as the dielectric fluid used in the transformer must be removed.
The present invention is directed to an apparatus used to decontaminate and thereby reclassify PCB-contaminated electrical apparatus which had operated with PCBs as the coolant dielectric fluid. In contrast to the prior art which has focused its attention primarily on the processes or methods for removing the PCBs from the electrical apparatus, the present invention is specifically directed to a compact apparatus having a size such that it can be placed into a building through the conventional spaces and doorways and can operate unattended while easily and effectively removing the PCBs from a contaminated electrical apparatus.
In the cleanup or reclassification of transformers, several processes or methods have been disclosed. A single refilling step is disclosed in U.S. Pat. No. 4,425,949, where the electrical apparatus, for example a transformer, is flushed with a heat stable fluid, such as perchloroethylene or Freon 113. Discussions of the problem of cleaning PCBs and PCB-contaminated electrical apparatus, particularly transformers, are found in U.S. Pat. Nos. 4,483,717 and 4,312,794.
U.S. Pat. Nos. 4,744,905 and 4,738,780 disclose retrofilling processes for replacing PCB-containing coolants in electrical induction apparatus with substantially PCB-free dielectric coolants. Both of these patents emphasize the steps utilized in a retrofilling process which require the repeated draining and refilling of the transformer to decontaminate the electrical apparatus and also emphasizes the specific dielectric fluids to be used in the method.
U.S. Pat. No. 4,685,972 discloses the process for removing PCBs from electrical apparatus. In the two drawings of this patent, the apparatus consists of a still for separating the dielectric fluid/solvent from the PCBs, a condenser for condensing the dielectric fluid/coolant and any water, a water separator to separate any water from the dielectric fluid/solvent and returning the water to the still, and a condensate tank for holding the condensed dielectric fluid/solvent before recirculating to the transformer. The two figures show alternate cooling units for the dielectric fluid which is disclosed as Freon 113.
The disadvantages of the processes and methods of the prior art are that they either generate a very large volume of contaminated fluid with more than 500 ppm of PCBs and require long periods of time to satisfy the non-PCB transformer standard or they include complicated processing equipment and steps for the removal of the PCBs. Some processes of the prior art require that the service of the electrical transformer be interrupted for long periods of time or many times during the decontamination process to satisfy the non-PCB transformer standard. Furthermore, the prior art disclose no provisions for heat management or heat recovery or use of temperature control in the electrical apparatus.
The apparatus of the present invention is applicable to a retrofill process or a continuous process for removal of the PCB-contaminated dielectric fluid and overcomes the disadvantages of the prior art methods and apparatus. It is an object of the apparatus of the present invention to provide heat management both in the electrical transformer during the reclassification period as well as the apparatus employed in the reclassification of the transformer. The heat used in the decontamination of the PCB contaminated transformer fluid, preferably incorporated into the distillation which separates the PCBs from the circulating dielectric fluid, is returned to the transformer to improve the rate of PCB removal therein from the transformer while the temperature within the transformer is continuously controlled.
It is another object of the present invention to provide an apparatus of compact size such that it can carry out the reclassification of transformers in buildings and the like. Often times the contaminated transformer is in the basement of a building restricted by doorways, elevator shafts or other restrictions which prevent the use of prior equipment but are not obstacles of the apparatus of the present invention. The apparatus of the present invention can be easily operated, on site and unattended without any substantial interruption in the operation of the contaminated transformer.